You heard it here first
I thought everyone was anyway now the O2 contract has ended.
I doubt 2 weeks time too, it's exclusive to o2 for longer than that!
On the 3 front - I didn't think they worked on 3? Whenever you look at an unlocked one (factory or jailbroken) it always states that it won't work on 3.
As a T-mobile user with an iPhone, I can tell you the lack of edge SUCKS! It's pretty much impossible to do anything over GPRS and MMS' always fail unless you have a 3G signal.
I heard a few months ago that T-Mobile had already started giving out iPhones to people threatening to leave as an incentive to stay with them.
This is true, IIRC 50-150 a week